The present invention relates in general to apparatus and methods for intramedullary fixation of abnormal bone, particularly applicable to femurs, tibia and humerus, and more particularly to intramedullary rods for fixation of impending pathological fracture, allograft fixation, or augmentation of osteopenic skeleton, incorporating means for feeding cement through the intramedullary rod to exit from the rod into surrounding bone tissue at variable locations.
Heretofore, various types of intramedullary rods have been provided for fixation of bones, such as for fixation of the femur and similar bones of appendages of the human body, particularly for fracture fixation. For example, Burstein patent Nos. 3,977,398 and 3,783,860 disclose intramedullary rods for use in fracture fixation, which in the later patent involves a rod which has longitudinal flutes but is closed at both ends, and in the earlier patent is in the form of a hollow tube having flutes and having castellated ends to provide sharp cutting surfaces and angled face guide projections.
The Branemark patent No. 4,065,817 discloses an arrangement wherein a perforated or slotted tube is inserted into a hole drilled in the bone and then the stem of a prosthesis is inserted in the hollow bore of the tube and cement is inserted to set the prosthesis in the tube, and cement is forced through openings into contact with the bone to secure the tube in place for a short term or mid term period.
The present invention is designed primarily for treatment of impending pathological fractures of bones from metastatic cancer, although it also is applicable to allograft fixation and augmentation of osteopenic skeleton.
The apparatus of the present invention has its therapeutic application for patients who are suffering from metastatic cancer to bone. For these patients, the interest is not directed at curing the cancer, but it is more directed at palliation from pathological fractures caused by the cancer. These fractures are both painful and cause loss of structural stability provided by the bones. The apparatus of the present invention is to provide for a quick and efficient means of dealing with these tumors in the bone.
An object of the present invention is the provision of an intramedullary rod and cement injection system for the treatment of abnormal bones, such as treatment of impending pathological fractures, allograft fixation, augmentation of osteopenic skeleton, and the like, including a novel configuration and structural assembly for a hollow intramedullary rod having selectively removable screw threaded plugs or open holes in a series of selectable discharge openings along the axial height of the rod for discharge of cement such as methylmethacrelate to surround the rod in adjacent bone tissue. A piston aided dispensing device similar to a caulking gun is coupled to the rod after insertion of the rod into the medullary and activated to force the low viscosity cement into the hollow interior bore of the rod for discharge through appatures where the plugs have been removed or holes are open. By augmenting the intramedullary rod with methylmethacrelate cement injected into the rod allowing it to surround the rod, this will provide for better fixation in areas which are involved with cancer, increasing the structural support of the involved bone, thermal kill of cancer, and an increasing of the structural strength of the intramedullary rod. The methylmethacrelate cement which exits around the rod at the desired level will fill defects caused by tumor or provide additional strength to the rod when it is used for osteoprotic bone or the fixation of allografts.
Another object of the present invention is the provision of a system as described in the immediately preceding paragraph, wherein the intramedullary rod is provided with a plurality of radially outwardly projecting thin fins spanning the vertical height of the rod to provide rotational stability, and wherein the rod is provided with a plurality of holes spaced vertically in each of the surface portions between pairs of the fins, normally closed by screw plugs or plugged with methylmethacrelate plugs, but which may be removed selectively prior to rod insertion to permit discharge of the cement into the desired surrounding bone area.
Yet another object of the present invention is the provision of a system as described in the two immediately preceding paragraphs, wherein the rod is a vertically elongated hollow tube and may be employed with externally threaded cylindrical plugs or hollow holes, positioned within the rod in selected corrolation with injection of cement to produce exit of cement into surrounding bone tissue at plural vertically spaced locations when required.
Another object of the present invention is the provision of a system as described in the immediately preceding paragraphs, wherein the rod is a vertically elongated hollow tube having a cross-sectional configuration of the rod such as to provide a pair of substantially parallel interior channels or tubes extending alongside each other along similar paths spaced diametrically opposite the center of the rod such that the remainder of the rod forms an I-beam type construction, with the holes spaced longitudinally along the channels or tubes which are normally closed by screw plugs and open in diametrically opposite directions from the channels.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.